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Abstract:

A method and system for controlling an engine includes a normal individual
cylinder fuel correction determination module determining normal pulse
mode individual cylinder fuel corrections in a normal pulse mode. The
system also includes a split pulse enable module operating the fuel
injectors in split pulse mode having a linear pulse and a ballistic pulse
smaller than the linear pulse. The system also includes a split pulse
individual cylinder fuel correction determination module determining
split pulse mode individual cylinder fuel corrections in the split pulse
mode. The system also includes a ballistic pulse adaptation module
adjusting ballistic pulse calibration values in response to the normal
pulse mode individual cylinder fuel corrections and the split pulse mode
individual cylinder fuel corrections to form adjusted ballistic pulse
calibration values.

8. A method as recited in claim 1 further comprising operating the engine
in response to the adjusted ballistic pulse calibration values.

9. A method as recited in claim 1 further comprising operating the engine
in a homogeneous charge compression ignition mode in response to the
adjusted ballistic pulse calibration values.

10. A method as recited in claim 1 further comprising operating the engine
in a stratified lean mode in response to the adjusted ballistic pulse
calibration values.

11. A method as recited in claim 1 wherein operating the fuel injectors in
split pulse mode having a linear pulse and a ballistic pulse smaller than
the linear pulse comprises operating the fuel injectors in split pulse
mode having a linear pulse less than about 8 milligrams of fuel and a
ballistic pulse less than about 3 milligrams of fuel.

13. A system method as recited in claim 12 further comprising a
subtraction module generating a difference of the normal pulse mode
individual cylinder fuel corrections and the split pulse mode individual
cylinder fuel corrections and wherein the ballistic pulse adaptation
module adjusts ballistic pulse calibration values in response to the
difference.

14. A system as recited in claim 13 further comprising a ratio module
determining a ratio of the normal pulse and a split pulse and wherein the
ballistic pulse adaptation module adjusts ballistic pulse calibration
values in response to the difference and the ratio.

15. A system as recited in claim 12 further comprising a condition monitor
module determining entry conditions.

16. A system as recited in claim 15 wherein the entry conditions comprises
a load condition.

17. A system as recited in claim 15 further comprising wherein the entry
conditions comprise a fuel per cylinder condition.

18. A system as recited in claim 15 wherein the entry conditions comprises
a spark ignition mode.

19. A system as recited in claim 15 wherein an engine control module
operates the engine in a homogeneous charge compression ignition mode in
response to the adjusted ballistic pulse calibration values.

20. A system as recited in claim 15 wherein an engine control module
operates the engine in a stratified lean mode in response to the adjusted
ballistic pulse calibration values.

Description:

FIELD

[0001]The present disclosure relates to engine control systems, and more
particularly to adjusting injection quantities of a fuel injector
suitable for injecting relatively small quantities.

BACKGROUND

[0002]The background description provided herein is for the purpose of
generally presenting the context of the disclosure. Work of the presently
named inventors, to the extent it is described in this background
section, as well as aspects of the description that may not otherwise
qualify as prior art at the time of filing, are neither expressly nor
impliedly admitted as prior art against the present disclosure.

[0003]As fuel economy and emissions requirements become stricter, new
combustion technologies are being developed. For example, engines are
being developed to not only run in spark ignition mode but also a
homogenous charge compression ignition (HCCI) mode. The HCCI mode
involves compressing a mixture of fuel and an oxidizer to a point of
auto-ignition. One of the modes may be selected based on engine speed and
load. Another advanced technology is the use of lean stratified
operation. Both of these technologies require relatively small fuel
injection quantities in the ballistic range of less than 5 milligrams of
injected fuel. The injector ballistic range is defined as the range of
injected quantities for which the pintal does not contact the opening
stop. Conventional fuel injection systems have a large variation of
injected fuel quantity when used for metering small quantities.

SUMMARY

[0004]The system according to the present disclosure operates the fuel
injectors using both a normal or linear pulse and a small or ballistic
pulse. Individual fuel control is then used to update the individual
injector small pulse calibration to allow for the small pulse to be used
with the newer combustion technologies.

[0006]In another aspect of the disclosure, a system for controlling an
engine includes a normal individual cylinder fuel correction
determination module determining normal pulse mode individual cylinder
fuel corrections for a normal pulse mode. The system also includes a
split pulse enable module operating the fuel injectors in split pulse
mode having a linear pulse and a ballistic pulse smaller than the linear
pulse. The system also includes a split pulse individual cylinder fuel
correction determination module determining split pulse mode individual
cylinder fuel corrections in the split pulse mode. The system also
includes a ballistic pulse adaptation module adjusting ballistic pulse
calibration values in response to the normal pulse mode individual
cylinder fuel corrections and the split pulse mode individual cylinder
fuel corrections to form adjusted ballistic pulse calibration values.

[0007]Further areas of applicability will become apparent from the
description provided herein. It should be understood that the description
and specific examples are intended for purposes of illustration only and
are not intended to limit the scope of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008]The present disclosure will become more fully understood from the
detailed description and the accompanying drawings, wherein:

[0009]FIG. 1 is a functional block diagram of an engine control system
according to the present disclosure;

[0010]FIG. 2 is a block diagrammatic view of the engine control module of
FIG. 1;

[0011]FIG. 3 is a flowchart of a method for operating the disclosure; and

[0013]The following description is merely exemplary in nature and is in no
way intended to limit the disclosure, its application, or uses. For
purposes of clarity, the same reference numbers will be used in the
drawings to identify similar elements. As used herein, the phrase at
least one of A, B, and C should be construed to mean a logical (A or B or
C), using a non-exclusive logical or. It should be understood that steps
within a method may be executed in different order without altering the
principles of the present disclosure.

[0014]As used herein, the term module refers to an Application Specific
integrated Circuit (ASIC), an electronic circuit, a processor (shared,
dedicated, or group) and memory that execute one or more software or
firmware programs, a combinational logic circuit, and/or other suitable
components that provide the described functionality.

[0015]The engine control system according to the present disclosure
operates may operate the gasoline engine in an SI mode, an HCCI mode or a
lean stratified mode. The HCCI mode reduces fuel consumption but is only
available over a limited range of engine torques and speeds. For example
only, the engine control system may operate the engine in the HCCI mode
at low to mid loads and low to mid engine speeds. The engine control
system may operate the engine in the SI mode at other loads and engine
speeds. The HCCI operating zones may be defined by operating maps in
calibration tables.

[0016]The engine may be a direct injection gasoline engine and may be
selectively operated in the stratified operating mode during the
transitions. To operate in the stratified operating mode, the fuel
injectors inject the fuel into an area of the cylinder, often a small
"sub-cylinder" at the top, or periphery, of the main cylinder. This
approach provides a rich charge in that area that ignites easily and
burns quickly and smoothly. The combustion process proceeds to a very
lean area (often only air) where the flame-front cools rapidly and
nitrogen oxides (NOx) have little opportunity to form. The
additional oxygen in the lean charge also combines with carbon monoxide
(CO) to form carbon dioxide (CO2).

[0017]Referring now to FIG. 1, a functional block diagram of an exemplary
engine system 100 is presented. The engine system 100 includes an engine
102 that combusts an air/fuel mixture to produce drive torque for a
vehicle based on a driver input module 104. The engine may be a direct
ignition engine. Air is drawn into an intake manifold 110 through a
throttle valve 112. An engine control module (ECM) 114 commands a
throttle actuator module 116 to regulate opening of the throttle valve
112 to control the amount of air drawn into the intake manifold 110.

[0018]Air from the intake manifold 110 is drawn into cylinders of the
engine 102. While the engine 102 may include multiple cylinders, for
illustration purposes, a single representative cylinder 118 is shown. For
example only, the engine 102 may include 2, 3, 4, 5, 6, 8, 10, and/or 12
cylinders.

[0019]Air from the intake manifold 110 is drawn into the cylinder 118
through an intake valve 122. The ECM 114 controls the amount of fuel
injected by a fuel injection system 124. The fuel injection system 124
may inject fuel into the intake manifold 110 at a central location or may
inject fuel into the intake manifold 110 at multiple locations, such as
near the intake valve of each of the cylinders. Alternatively, the fuel
injection system 124 may inject fuel directly into the cylinders. The
fuel injection system 124 may include a fuel injector 125. The fuel
injector operates using a pulse. Typical fuel injectors operate in a
normal mode with a pulse from the engine control module 114 that opens
the fuel injector to inject an amount of fuel that is directly related to
the time of the pulse. In the present disclosure, the pulse from the
engine control module 114 is divided into a ballistic region that
corresponds to a small pulse and a linear region that is greater than the
ballistic region. Both the amount of fuel and the time associated with
the pulse in the linear region are greater than the amount of fuel and
the time associated with the opening of the fuel injector corresponding
to the ballistic pulse. By way of example, a ballistic pulse may inject
about one to about three milligrams of fuel. A linear pulse may include
quantities greater than about 6 mg. The normal pulse may thus be several
times greater than the small pulse.

[0020]As illustrated, one fuel injector 125 is provided. However, those
skilled in the art will recognize that multiple fuel injectors
corresponding to the amount of cylinders in the engine may be provided.
As mentioned above, the linear region is typically very accurate and thus
has a low standard deviation. The ballistic region typically has a high
standard deviation. As will be described below, the error associated with
ballistic region is significantly reduced using the teachings provided in
the present disclosure. By controlling the small or ballistic pulse
region, misfires may be prevented in various combustion technologies.

[0021]The injected fuel mixes with the air and creates the air/fuel
mixture in the cylinder 118. A piston (not shown) within the cylinder 118
compresses the air/fuel mixture. Based upon a signal from the ECM 114, a
spark actuator module 126 energizes a spark plug 128 in the cylinder 118,
which ignites the air/fuel mixture. The timing of the spark may be
specified relative to the time when the piston is at its topmost
position, referred to as to top dead center (TDC).

[0022]The combustion of the air/fuel mixture drives the piston down,
thereby driving a rotating crankshaft (not shown). The piston then begins
moving up again and expels the byproducts of combustion through an
exhaust valve 130. The byproducts of combustion are exhausted from the
vehicle via an exhaust system 134.

[0023]The intake valve 122 may be controlled by an intake camshaft 140,
while the exhaust valve 130 may be controlled by an exhaust camshaft 142.
In various implementations, multiple intake camshafts may control
multiple intake valves per cylinder and/or may control the intake valves
of multiple banks of cylinders. Similarly, multiple exhaust camshafts may
control multiple exhaust valves per cylinder and/or may control exhaust
valves for multiple banks of cylinders.

[0024]The time at which the intake valve 122 is opened may be varied with
respect to piston TDC by an intake cam phaser 148. The time at which the
exhaust valve 130 is opened may be varied with respect to piston TDC by
an exhaust cam phaser 150. A phaser actuator module 158 controls the
intake cam phaser 148 and the exhaust cam phaser 150 based on signals
from the ECM 114. The lift actuator module 120 adjust the amount of valve
lift hydraulically or using other methods.

[0025]The engine system 100 may include an exhaust gas recirculation (EGR)
valve 170, which selectively redirects exhaust gas back to the intake
manifold 110. The engine system 100 may measure the speed of the
crankshaft in revolutions per minute (RPM) using an RPM sensor 180. The
temperature of the engine coolant may be measured using an engine coolant
temperature (ECT) sensor 182. The ECT sensor 182 may be located within
the engine 102 or at other locations where the coolant is circulated,
such as a radiator (not shown).

[0026]The pressure within the intake manifold 110 may be measured using a
manifold absolute pressure (MAP) sensor 184. In various implementations,
engine vacuum may be measured, where engine vacuum is the difference
between ambient air pressure and the pressure within the intake manifold
110. The mass of air flowing into the intake manifold 110 may be measured
using a mass air flow (MAF) sensor 186.

[0027]The ECM 114 may calculate measured air per cylinder (APC) based on
the MAF signal generated by the MAF sensor 186. The ECM 114 may estimate
desired APC based on engine operating conditions, operator input or other
parameters. The throttle actuator module 116 may monitor the position of
the throttle valve 112 using one or more throttle position sensors (TPS)
190. The ambient temperature of air being drawn into the engine system
100 may be measured using an intake air temperature (IAT) sensor 192. The
ECM 114 may use signals from the sensors to make control decisions for
the engine system 100.

[0028]To abstractly refer to the various control mechanisms of the engine
102, each system that varies an engine parameter may be referred to as an
actuator. For example, the throttle actuator module 116 can change the
blade position, and therefore the opening area, of the throttle valve
112. The throttle actuator module 116 can therefore be referred to as an
actuator, and the throttle opening area can be referred to as an actuator
position.

[0029]Similarly, the spark actuator module 126 cane be referred to as an
actuator, while the corresponding actuator position is amount of spark
advance or retard. Other actuators include the EGR valve 170, the phaser
actuator module 158, and the fuel injection system 124. The term actuator
position with respect to these actuators may correspond to, EGR valve
opening, intake and exhaust cam phaser angles, air/fuel ratio,
respectively.

[0030]Referring now to FIG. 2, a functional block diagram of the engine
control module 114 is set forth in further detail. The engine control
module 114 includes a condition monitor module 210. The condition monitor
module 210 monitors the entry conditions for reducing ballistic range
fuel metering error. Entry conditions may include setting the combustion
mode to conventional spark ignited mode and performing the method at a
light load or at an idle speed.

[0031]The condition monitor module 210 may be in communication with a
normal individual cylinder fuel correction (ICFC) determination module
212. The normal individual cylinder fuel correction may correspond to
conventional fuel injector operating using a single normal-size fuel
pulse to inject the entire desired quantity of fuel it should be noted
that the individual cylinder fuel corrections are determined for each of
the cylinders and thus for each of the fuel injectors of the engine.

[0032]The engine after the normal operating mode may operate in a split
injection pulse mode. A split pulse enable module 214 operates the fuel
injector in a split injection pulse mode. The split injection pulse mode
may have a ballistic range that corresponds to a small pulse such as 1-3
milligrams of fuel and a normal pulse range that corresponds to the total
amount of fuel required minus the small pulse. A normal pulse may be
about 10 milligrams.

[0033]The individual cylinder fuel corrections are determined for each of
the cylinders in the split pulse ICFC determination module 216. It should
be noted that the individual fuel corrections determined using the normal
pulse operation and the split pulse operation may be stored in a memory
218.

[0034]A subtraction module 220 may subtract the normal individual cylinder
fuel corrections from the split pulse individual cylinder fuel
corrections. In block 222, a ratio module may determine the ratio of the
normal pulse to the split pulse. The ratio module may then multiply the
difference of the normal pulse and the split pulse individual cylinder
fuel corrections. In block 224, the ballistic pulse adaptation module
adapts the ballistic pulse calibration based upon the weighted difference
determined in block 222.

[0035]Referring now to FIG. 3, a method for adjusting the ballistic range
fuel metering area is set forth. In step 310, a conventional combustion
mode is entered if the engine is not operating in a conventional
combustion mode. In step 312, a determination of the entry conditions for
the method is performed.

[0036]If the entry conditions are not met in step 312, step 310 is again
performed. When the entry conditions are met in step 312, step 314 stores
a ballistic pulse calibration. The ballistic pulse calibration may be
updated periodically as will be further described below. An initial
calibration may be provided and stored during the manufacture of the
vehicle. In step 316, the individual cylinder fuel corrections (ICFC)
using the normal single fuel pulses may be stored in the memory.

[0037]In step 318, the injection pulse is split into a ballistic pulse and
a normal or linear pulse. The size of the ballistic pulse, as mentioned
above, may vary from about one to about three milligrams of fuel. In step
320, the ballistic pulse is subtracted from the total fuel required to
obtain the linear pulse. The pulse may correspond to a time size of the
pulse or to a weight of the injected fuel.

[0038]In step 322, a split pulse operation of the vehicle is enabled. The
split pulse operation operates with the linear pulse and the ballistic
pulse. In step 324, the individual cylinder fuel corrections are stored
in the memory when the split pulse is enabled.

[0039]In step 326, the normal individual cylinder fuel corrections are
subtracted from the split pulse individual fuel corrections to obtain a
difference. The difference may be referred to as a ballistic pulse error.
In step 328, the difference from step 326 is weighted. The weighting may
be of the ratio of the normal pulse to the split pulse. In step 330, the
ballistic pulse calibration of step 314 is adjusted using the weighted
difference. Repeating the process periodically provides continual
updates. In step 332, the adjusted ballistic pulse calibration is used in
the operation of the fuel injectors and thus the operation of the engine.
The operation of the engine may use the adjusted ballistic pulse
calibration in a lean stratified mode or in an HCCI mode. The adjusted
ballistic pulse calibration may be stored and continually adjusted using
the above-mentioned process. By continually adjusting the ballistic pulse
calibration, the risk of misfire due to fueling errors is reduced due to
the adaptive learning techniques, and overall combustion robustness and
efficiency is improved.

[0040]Referring now to FIG. 4, a plot of injected mass versus injection
duration is illustrated. Low-injection durations between about 0.2 and
about 0.3 correspond to a ballistic region 410. As mentioned above, the
ballistic region has high injector to injector variability of fuel mass
metering.

[0042]Those skilled in the art can now appreciate from the foregoing
description that the broad teachings of the present disclosure can be
implemented in a variety of forms. Therefore, while this disclosure has
been described in connection with particular examples thereof, the true
scope of the disclosure should not be so limited since other
modifications will become apparent to the skilled practitioner upon a
study of the drawings, the specification and the following claims.